Method and apparatus for manufacturing pencils



Z. LORENIAN April 30, 1957 3 Sheets-Sheet 1 Filed March 31, 1952 FIG. 3

Z. LORENIAN April 30, 1957 METHOD AND APPARATUS FOR MANUFACTURINGPENCILS v s Sheets-Sheet 2 Filed March 31, 1952 April 30, 1957 z.LORENlAN METHOD AND APPARATUS FOR MANUFACTURING PENCILS Filed March 51,1952 3 Sheets-Sheet 5 United States atent- O METHOD AND APPARATUS FORMANUFAC- TURING PENCILS Zareh Lorenian, Milan, Italy Application March31, 1952, Serial No. 279,496 12 Claims. (Cl. 18-13) The presentinvention relates to a method and to apparatus for manufacturingpencils. This application is a continuation-in-part of myapplication'Serial No. 19,788, filed April 8, 1948, which has now becomeabandoned.

At present pencils are made by one of the four following methods:

1. The lead (marking material) is placed centrally between the twohalves of a Wooden sheath or envelope which are glued together along theentire length of the encil. P 2. The lead is sheathed in an envelopemade by rolling a paper band around the lead. This envelope'isprogressively unrolled as the lead wears down.

3. The pencil may be formed by the lead itself without any specialenvelope, the lead being simply covered with an adequate coat ofvarnish.

4. A permanent sheath or envelope is made from wood, plastic, or metal,and changeable leads are introduced into and fed through this envelopeby mechanical feeding means.

The first and second methods of manufacturing a pencil have manydisadvantages. They consume a large amount of good quality wood, such ascedar, linden, poplar, etc. or a special type of paper. They require aseries of expensive operations, and demand complicated machines, andskilled workmanship. Moreover, in pencils made by either the first orsecond method the leads are subject to easy breakage on account ofdrying of the wood, or original unprecise dimensioning of the diameterof the channel in which the lead is placed, or because of imperfectgluing, or imperfect rolling of the paper sheathing band.

The third method is limited to use in producing special purpose pencils.whether the varnish coating be applied by immersion, pressure, or byforced coating.

The fourth method means an initial relatively large investment becauseof the expensive sheath or envelope. Moreover, in mechanical pencils thefeeding mechanism often jams, or the lead breaks. Such pencils haveother drawbacks also.

The primary object of the present invention is to provide a process andapparatus which permit the manufacture of pencils, or coated markingdevices, by a simple, inexpensive process which avoids all thedisadvantages of the prior methods mentioned above.

A concomitant object of the invention is to provide a process andapparatus for making pencils from relatively inexpensive sheathingmaterials so that the pencils can be sold at a price that will comparefavorably with pencils produced by either of the first two conventionalmethods listed above.

A further object of the invention is to provide a process and apparatusfor making pencils in which the sheath will be adhered to the lead morefirmly than by any previously known process of making pencils.

Other objects of the invention will be apparent here- Moreover, itrequires expensive labor,

2,790,202 Patented Apr. 30, 1957 inafter from the specification and fromthe recital of the appended claims.

In the process and apparatus of making pencils according to thepresentinvention, sheathingmaterial in a thermoplastic state is fed over andaround the lead to adhere it to the lead. The lead itself may be inrigid pieces, or it may be shaped in thermoplastic condition to form thecore of the pencil before the thermoplastic sheath covers it. Inpracticing the invention, apparatus is employed having a pair of nozzlesarranged one within the other.

The rigid marking core or the thermoplastic marking material is fedthrough the inner nozzle and the sheath material is fed through theouter nozzle both being continuously fed by extrusion screw presses orthe like. Both marking material and sheath progress in the samedirection. The rigid marking core, or the thermoplastic markingmaterial, is accurately guided in the marking core nozzle over the finalpart of its length. The warm sheath material progressing in its nozzleglides over the marking core nozzle which is thin-walled. On reachingthe zone and in the zone where it unites with the marking core, whichzone is at a point spaced from the beginning of the narrowest crosssection of the sheath material nozzle, the sheath material is pre-shapedinside to correspond to the cross section of the marking core in such amanner and so far that the sheath material, almost without changing itsinner cross section and its direction, and without damaging the markingcore, is deposited by gliding'movement on and aroundthe marking core andis united therewith. The sheathed marking core is then guided throughthe cylindrical outlet of the external nozzle whereby the pencil obtainsdefinitive shape.

The portion of the sheath material nozzle adjacent its discharge end hasa cylindrical bore. The marking core nozzle terminates at a distancefrom the beginning of the cylindrical bore of the sheath materialnozzle. The marking core nozzle has at least in the part which isadjacent its discharge end a wall thickness smaller than the diameter ofits bore. The marking core nozzle ends before the sheath material nozzleand is preferably sharp ened externally at its discharge end. Themarking core nozzle over some length adjacent its discharge end has abore whose cross section corresponds to the cross section of the markingcore.

If the marking cores, which are to be sheathed, are rigid, for exampleceramic marking cores, said cores may be coated with an adhesive beforeuniting them with the sheath material to give a stronger adhesionbetween the rigid marking core and the sheath material.

By using the same principle as is employed in sheathing the lead, thesheathed pencil may also be coated with a thin thermoplastic externalcoating after the marking core has been united with the sheath and whilethe sheath is still in warm plastic condition. For this purpose a thirdnozzle is provided. The thermoplastic external coating material isintroduced, for example, by a feed screw into this third coating nozzlewhich preferably forms part of, or is secured in, the sheath materialnozzle. The thermoplastic coating material slides on the sheath materialnozzle which is thin-walled at its discharge end; and the third nozzleis pro-shaped inside almost to the cross section of the pencil so thatupon reaching the zone and in the zone Where the coating material uniteswith the pencil, which zone is at a point spaced from the beginning ofthe narrowest cross section of the coating nozzle, the coating materialis pre-shaped insideto the cross section of the pencil in such mannerthat almost without changing its inner cross section and its directionand without damaging the pencil, the coating material is deposited witha gliding movement on and around the greases pencil and is unitedtherewith. The'coatedpencil-is their guided through the discharge end ofthe coating nozzle which is preferably cylindrical inside, so that thepencil obtains its finished covering.

In the drawings:

Fig. 1 is an axial section through apparatus builtaccording to oneembodiment of this invention for production of pencils with rigid cores;

Fig. 2 is a fragmentary section, similar to part of Fig. 1, showing partof a modified form of nozzle for feeding the sheathingmaterial over thecore;

Fig. 3 is a fragmentary section similar to the sections of Fig. 2,showing a noiz'le for the core through-which more than one core can besimultaneously fed itito'th' nozzle for the sheathingmatei'ial;

Fig. 4 is a transverse section of a pencil having two leads such as maybe produced by the apparatus ofFig. 3;

Fig. 5 is a transverse section of a pencil with three leads in its corewhich may alsob'e'produced by the apparatus of Fig. 3;

Fig. 6 is an axial section,-showing amddifie'd roan of apparatus, inwhich the rigid lead core is c'over'e'd'with an adhesive before itsenvelopmeht by the sheathing'fria terial; I Fig. 7 is an axial section,similar to'Fi-g; barren-git a further embodiment of the invention inwhich the care material is in plastic form and is fed concentrically tothe plastic sheathing material, and in which both the'co'r'e' materialand the sheathing material are fed by means of screws and in which athird feed screw is placed at the side of the sheathingnozzle fordeliveringa coating niaterial onto the sheathed pencil;

Fig. 8 is a section similar to Fig. 7 showinga still fur thermodification of the invention in which the core and the coating inplastic form are carried into the apparatus in directions at rightangles to the directions of movement of the sheathing material; and

Fig. 9 is a section on the line AA of Fig. 8 looking in thedirection ofthe arrows.

Referring now to the drawings by numerals of reference, 11 denotes thecore of the pencil, the lead, the marking material. In some instances,as will appear hereinafter, rigid, preformed lead is used as the core;and in other instances the core is formed from thermoplastic markingmaterial in the apparatus of the present invention in the process ofmaking the pencil. The cover or sheath of the pencil is denoted at 12..16 denotes the sheathing material in its thermoplastic state. 13 denotesthe nozzle for forming and shaping the sheathing material; and 18designates the nozzle through which the lead or marking core 11 is fed.15 designates a support in which both nozzles are mounted. The nozzle 18has a bore to suit the shape of the lead 11. The nozzle 13 is providedwith a bore to produce the desired outside shape of the sheath.

y In the apparatus of Figs. 1 to 3 inclusive, the nozzle -13 is securedin the body 15 by means ofa nut 14. This-nut engages a shoulder onnozzle 13'and threads into body 15. The nozzle 18 is fastened by meansof a nut- 19 in the bodylS of the apparatus. Thenozzle 18 has anexternal shoulder that fits in a correspondingly-shaped recessin body lSand the nut 19 threads into the body 15 to abut at its inner end againstthe outer face of nozzle 18.

In the apparatus shown in Fig. 1, rigid pre-formed leads are used forforming the cores of the pencils. -In Fig; 1 two such leads are showndisposed one abutting the other. When rigid leads such as are shownin'Fig. 1 are used, the lead, which is to form the core the next pencilto that being manufactured in body 15, is held in tube 21 which is alsosecured to body 15 by the nut 19. This tube is counterbored at itsdischarge end to receive the inlet end of nozzle 18; and it is formedwith an external shoulder that fits into a counterbore in the inner endof nut 19. w

The nozzle 13 has a part 17 whose bore is cylindrial correspondingto theexternal shape of the pencil which is to be produced.

The body 15 of the apparatus is threaded into the cylin- (lot 22 of aconventional screw press by means of the thread 20. 23 indicates a partof the feed screw of the press which feeds the sheathing material intothe body 15 and nozzle 13.

The body member 15 is cored out with a right-angle bore to permit flowof the sheathing material 16 therethrough around nozzle 18 and intonozzle 13.

The nozzle 18 for the core 11 consists of an upper thicker part and alower very thin-walled part. The wall thickness of the lower part issmaller than the diameter of the bore of nozzle 18. The diameter andshape of the nozzle 18 corresponds at least adjacent its discharge endto the transverse shape of the core 11, in order that the core may besecurely held and fed into the sheathing material 16.

The nozzle 13 has a bore which isconical at its inlet end and whichtapers toward the cylindrically-bored part 17. In order to attain smoothtransition of the sheathing material from around the nozzle 18 to thecore 11 with the least possible change in transverse section, thethinwalled nozzle 18 is preferably further thinned at its discharge end.Furthermore, the discharge end of the nozzle 18 lies at a distance fromthe beginning of the part17'of the nozzle 13 which is the narrowesttransverse section of nozzle 13. The nozzle 18 is so arranged in thenozzle 13 that the thermoplastic sheating material 16 can glide asufiicient distance on the nozzle 18 and can cover completely thethinned walled nozzle 18 so that it will join smoothly the lead 11 asthe lead emerges from the discharge end of the nozzle 18.

Heating coils 24 surround both the cylinder 22 and the body 15 to keepthe sheathing material in thermoplastic condition until the pencil isformed. Channels 25 are also provided in the body 15 for coolant or atemperaturecontrolling medium. The coolant, or temperature-controllingmedium is introduced into the channel 25 through an inlet port 26 in asleeve which is welded to body 15. It is carried away through an outlet27in the same sleeve. The coolant or temperature-controlling mediumhelps set the sheathing material so that as the sheathed lead 11 leavesthe discharge end of nozzle 13, the sheath 12 is firm and securelyattached to lead 11, forming with lead 11 a pencil.

Fig. 2 shows a modification in which the discharge end of the nozzle 18is positioned in the cylindrical part 17 of the nozzle 13 but still at alarge distance from the discharge end of the nozzle 13, as compared withFig. l where the end of nozzle 18 is positioned in the conical portionof the bore of the nozzle 13. The nozzles 18 in both embodiments (Figs.1, 2) terminate at a distance from the beginning of the narrowest crosssection of nozzle 13.

Fig.3 shows a partof a nozzle 18 through which two leads 11a and 11b, orthe material for forming these leads, may simultaneously be fed into thesheathing nozzle 13 to be covered by the'sheathing material 16. The twoleads may be differently colored, or one may be hard and the other soft,etc.

Fig. 4 shows a section of a completed pencil having two leads 11a and11b.

Fig. 5 shows a similar section of a pencil with three diiferent leads11a, 11b and Tile.

Fig. 6 shows how the lead'11 can be coated in the tube 21 with anadhesive 58 for more securely binding the sheathing to the lead. Herethe adhesive 58 is fed throu h the tube 59 by means of apparatus notshown and through a nozzle 60 which corresponds in principle to thepreviously described nozzle arrangement for feeding the sheathingmaterial'over the lead. Here the nozzle 59 is threaded into a hole inthe side of the tube 21.

. Fig. 7 shows a section through an apparatus for.mak ing a pencil whereboth the marking material and the sheath are thermoplastics. Here twofeed screws are provided, arranged concentrically to one another, theinner one 33 serving for feeding the thermoplastic marking material 34which is formed in the nozzle 18 into the lead of the pencil. The screw33 operates in nozzle 18. This nozzle has a sleeve 36 surrounding it andwelded to the nozzle 18 at its lower end. The outer screw 23 serves forfeeding the sheathing material 16 and operates in the nozzle 13 which ismounted in a sleeve 37. The arrangement of the nozzle 18 in the nozzle13 is in principle the same as in Fig. 1. Between the sleeve 36 andnozzle 18 is a channel 35 for the temperature controlling medium.Between nozzle 13 and sleeve 37 is a channel 25 also for the coolant ortemperature-controlling medium. 26 and 27 denote, as before, the inletand outlet, respectively, for channel 25. The bore of nozzle 18 isshaped to receive feed screw 33 and tapers gradually to the desireddiameter of the finished pencil lead, the final portion of the bore ofthe nozzle, adjacent its discharge end, being preferably madecylindrical to properly form and hold the marking core, or lead 11. Thebore of nozzle 13 in Fig. 7 is shaped similarly to the bore of nozzle 13shown in Fig. 1 so that the thermoplastic sheathing material 16 flowssmoothly over the nozzle 18 and joins the lead 11 emerging from nozzle18 smoothly without undue pressure. The nozzle 18 is screwed at 40 intothe lower end of a channeled sleeve 36 that contains the feed screw 33.

Pressure regulating and discharge tubes provided with bores 39 aremounted in sleeve 37. These serve to control the pressure of thesheathing material in the zone of juncture of the core 11 and thesheathing material 16. The pressure nipples 38 can for this purpose beinterchanged with nipples of smaller or larger bore. The pressureregulating and pressure escape fittings 38 are provided with valves 62.The valves 62 are held closed under the pressure of springs 41 and caneither be adjusted by changing the springs 41 or through threading ofthe caps 61 inwardly or outwardly. Excess sheath material can escapethrough valves 62 if the pressure in the material exceeds an adjustedlimit, so that the pressure is regulated accordingly.

, Fig. 7 also shows means for applying a plastic coating material 46over the sheath 12 after the pencil has been formed. The thermoplasticcoating material is fed over sheath 12 by a feed screw 44 which operatesin a sleeve 45. This sleeve is provided with a channel 43 for atemperature-controlling medium. The duct through which the temperaturecontrolling medium is carried is indicated at 49. The feed screw 44serves to feed the thermoplastic outer covering material 46 through ahole in the lower end of nozzle 13 around the discharge end of nozzle 13and into a nozzle 56. To insure smooth juncture of the coating materialwith sheath 12, the cylindrical part 17 of the nozzle 13 has a verynarrow wall thickness adjacent its discharge end as is indicated at 47.The nozzle 17 ends at a distance from the smallest transverse section ofthe outer nozzle 56. The transverse section of the cylindrical part ofthe outer nozzle corresponds very closely in diameter to that of thetransverse section of the pencil. The outer nozzle 56 is secured bymeans of screws 57 to the body 37. Pressure regulating fittings 38 aresecured in sleeve 37 and nozzle 56. In this embodiment of the inventionthe channel for the coolant or temperature-control medium extends intonozzle 56 as well as through sleeve 37.

Figure 8 shows another arrangement in which the feed screw 33 for thethermoplastic marking material 34 is positioned so that the markingmaterial 34 is fed from the side through a sleeve 36, an adaptor 52, andthe curved portion 53 of a nozzle 18. The feed screw 33 rotates in thesleeve 36. The curved section 53 of nozzle 18 has a streamlinedreinforcing projection 50 onits backside which also makes it possiblefor the sheathing material 16 to readily slide thereon. The

It comprises a ring 54 which is connected by integral spokes 55 withpart 53 and which is set into a suitable recess in the sleeve .37. Thetemperature-controlling medium for the sleeve 36 is fed into a channel35 in that sleeve through a duct 51.

The thermoplastic sheathing material is fed, as before, by a rotary feedscrew 23 driven by conventional means. Sleeve 37 has a conical bore inits upper portion which tapers to the desired outside diameter of thepencil and then becomes cylindrical. The discharge end of nozzle 18 issituated some distance above the cylindrical section of the bore ofsleeve 37 so that the thermoplastic sheathing material may glidesmoothly over the tapered outside surface of nozzle 18 and smoothly joinand cover the marking material 11 emerging from nozzle 18.

A thermoplastic coating material 46 is applied over the sheathed pencil.This coating material is supplied through a sleeve 45 which is mountedin sleeve 37 at right angles thereto. A feed screw 44 rotates in sleeve45 to forward the hot thermoplastic coating material through the sleeveinto a nozzle 56 that is secured in sleeve 37 (nozzle 13). Sleeve 37(nozzle 13) as before, has a conical portion which receives the coatingmaterial and which merges with a conical bore in nozzle 56. The conicalsection of the bore of nozzle 56 merges into a cylindrical bore sectionof that sleeve at a point spaced far enough from the discharge end ofnozzle 56 to .form the coating closely around sheath 12 of the penciland to adhere the coating firmly to the sheath so that the coated pencilemerges from the discharge end of nozzle 56.

Sleeve 45 is provided, as before, with a channel 43 for a coolant ortemperature-controllmg medium. This is supplied through port 49. Sleeve37 is provided, as before, with a channel 25 for a coolant ortemperature-controlling medium which is supplied through a duct 26.

The method of operation of the apparatus in the case of rigid leads 11will be obvious from the preceding description but may be briefly summedup here, reference being had to Figs. 1 to 6 inclusive. Out of amagazine which is not shown, the leads 11 are fed through the sleeve ortube 21 into the nozzle 18 by means of conventional feed apparatus (notshown). The hot thermoplastic sheathing material 16 is fed in a plasticstate by the feed screw 23 into the body 15. The sheathing material 16is so fed in the body and the nozzle 18 is so arranged that thesheathing material slides for a sufiicient length over the wholeperiphery of the thin-walled nozzle 18 so that the sheathing material 16and the lead 11 move in the same direction and with the same speed inthe direction of the narrowest section of the outer nozzle 13, and thesheathing material 16 slides from the thin-walled nozzle 18 onto thelead 11. Since both lead and sheathing mate rial are moving in the samedirection and the ditference between the diameter of the lead and theinner transverse section of the sheathing material is very slight andsince the sheathing material is deposited on the lead at a distance fromthe beginning of the narrowest section of the sheathing nozzle 13, thesheathing material is deposited securely on and about the lead withoutchange or the inner transverse section and direction of the sheathing.material and without essential pressure transmission and without injuryto the lead. The bore of the cylindrical part of the nozzle 13 conformsto the desired outside shape and diameter of the pencil. Hence, thesheath 12 is firmly and smoothly secured to lead 11 and the finishedpencil emerges from the nozzle 13.

Where it is desirable to employ an adhesive to secure the sheathingmaterial firmly to the lead, an arrangement, such as shown in Fig. 6 maybe employed. Here, the adhesive is carried through a tube 59 and througha nozzle arrangement 60 which corresponds in principle to thepreviously-described nozzle arrangement for sheath-- ing rigid leadswith sheathing material.

7 When the leadis produced-from a, thermoplastic marking material theoperation is in principle the same; The marking material 3Q (Figs. 7, 8)is, for example, fed by means of the rotaiyfeed screw 33, which operatesin the a sleeve 36, into the nozzle 18 andis formed inthis nozzle intothe marking core 11. The sheathing material 16' is advanced by the feedscrew 23, The nozzle 18 is so arranged that the sheathingmaterial'slides a sufiicient distance on the whole periphery of thenozzle 18 and that its inside is pre formed to the transverse section ofthe .lead. The further operation corresponds completely to thatdescribed for rigid leads.

Should it be desired to provide the finished pencil in the same workingoperation with an outer covering then the coating material which isformable by heat and ressure is fedby means ofa rotary feed screw 44(Figs. 7' and 8) which operates in a sleeve 45. Since at the instant of;introduction ofjthe outer coating onto sheath 12, the pencil is srill ina plastic easily formable state, the nozzle arrangement for the plasticcoating corresponds completely to the previouslydescribed nozzlearrangement for forming the sheath over the lead, The cylindrical part17 of the nozzle 13 has on this account a very small wall thickness 47for a sufiicient length for the smoothunion of the pencil with the outercovering, The material of the outer covering46 is formed in its movementontothe sheathed pencil. Since the union of the outer covering 48 and ofthe pencilis at a sutficient. distance. from the narrowest portion ofthe nozzle 56,. whichgivesthe outer covering its outer form, thejuncture and'the deposit of the outer covering material takes place onthe. pencil without substantialtransmission of pressure in a directionperpendicular to the pencil axis.

While the-invention has been described in connection with severaldifierent embodiments thereof it will be understoodthat it is capable offurther modification, and this application is intended to cover anyvariations,-uses, or adaptations of the invention following, in general,the principles of the invention and including such departures from thepresent disclosure as come within known or customary practice in the artto which the invention pertains and as may be applied to the essentialfeatures hereinbefore set forth and as fall within the scope of theinvention or the limits of the appended claims.

Having thus described my invention, what I claim is: 1. The method ofmanufacturing pencils by continuous extrusion of material throughcoaxial nozzles, which comprises continuously forwarding a marking-coremedium in one and the same direction through a thin walled a elongatedand straight tube forming part of the inner nozzle and having over mostof its length adjacent to its outlet at constant cross section nearlyequal to that of the pencil core; continuously feeding and. forwardingthrough the outer nozzle a thermoplastic sheath materialin heated andplasticized conditionalong the forwarding direction of the markingmedium around the tube and pie-shaping the sheath material insymmetrical relation to the tube along said length of the tube thusforming in the preshaped sheath material a hole of the same crosssection as the core medium; glidingly depositing the sheath materialonto and around the core medium along an axially elongated zone confinedwithin the outer. nozzle, maintaining the radial component of pressurein the sheath material smaller than the axial component of pressureduring the entire passage of the sheath material from along the tube tothe outer-nzzle outlet, and maintaining the sheath material confined toa constant cross section along an elongated path adjacent to theouter-nozzle outlet to externally shape the sheath to its final shape,whereby the 8 ing-core material in one and the same direction and inheated andplasticized condition through a" thin-walled, elongatedandstraight nozzle tube forming the outlet part of the inner nozzle toobtaina marking core of final shape where the'core material emerges fromthe outlet of' the tube; continuously forwardingthroughthe ou ter nozzleathermoplastic sheath material in heated and plasticized condition alongthe forwarding direction of the core material around the tube and preshaping the sheath materialin symmetrical relation to most of the lengthof the tube adjacent to its outlet thus forming in the sheath material ahole of substantially the same cross section as the core material;glidingly depositing the sheath material on and around the core materialalong an axially elongated zone confined within the outer nozzle,maintaining theradial component of pressure in said sheath materialsmaller than the axial component of pressure during the entire passageof the sheath material from along the tube to the outer-nozzle outlet,and maintaining the sheath material confined to a constant cross sectionalong an elongated path adjacent to said outer-nozzle outlet toexternally shape the pencil to its final shape, whereby thecorernaterial and sheath material in the finished pencil are intimatelybonded to each other. i

3. In the method of manufacturing pencils according to claim 1, thesteps of composing" the marking-core medium of a plurality ofdifferently colored rigid parts, and simultaneously feeding said coreparts axially beside each other through the inner-nozzle tube, whereby aplural-color pencil isproduced.

4. The method of maufacturing pencils by an extru sion screw presshaving coaxial inner and outer nozzles respectively, which comprisesfeeding a rigid marking core material in-one and the same directionthrough a thin-walled, elongated and straight nozzle tube forming partof said inner nozzle, and coating said core material with an adhesive asthe core material is moving into said nozzle tube; continuously feedingand forwarding through the outer nozzle a thermoplastic sheath materialin heated and plasticized condition along the forwarding direction ofthe core material around the tube and pre-shaping the sheath material insymmetrical relation to the tube along most of the length of saidtubeadjacent to its outlet thus forming in the sheath material a hole ofsubstantially the same cross section as the adhesively coated corematerial; glidingly depositing the sheath material onto and around theadhesively coated core material at the point where both materials meet,maintaining the radial component of pressure in the sheath materialsmaller than the axial component of pressure during the entire passageof the sheath material from along the tube to the outer-nozzle outlet,and maintaining the sheath material confined to a constant cross sectionalong an elongated path adjacent to the outer-nozzle outlet toexternally shape the sheath to its final shape, whereby the corematerial and sheath material in the finished pencil are intimatelyjoined with each other by said adhesive.

5. The method according to claim 1, which comprises flowing athermoplastic coating material in heated and plasticized condition andin film thickness onto and around the sheath material while the sheathmaterial in heated condition passes out of said path of confined crosssection, confining the coated material along an elongated additionalpath to a constant cross section corresponding to that of the finishedpencil, and maintaining the radial component of pressure in the coatingmaterial smaller than the axial component of pressure during the entirepassage of the coating material from the point .where it meets thesheath material to the end of said additional path.

6. Apparatus for manufacturing pencils by continuous extrusioncomprising, in combination, an outer nozzle having a bore, an'innernozzle having an outlet and Jhaving adjacent to said outlet and withinsaid borea straight elongated and thin-walled tube of uniform crosssection corresponding nearly to that of the finished marking core; meansfor continuously supplying marking medium through said inner nozzle toemerge from said tube outlet; means for continuously forwardingthermoplastic sheath material through said outer nozzle; saidinner-nozzle tube having over most of its length within saidouter-nozzle bore a Wall thickness which is a fraction of the innerwidth of the tube and which tapers at said outlet to a line edge havingthe shape and size of the core of the finished pencil; said outer-nozzlebore extending coaxially and symmetrically around said tube over most ofsaid tube length and extending axially beyond said inner-nozzle outlet,said bore having a portion tapering toward the outer-nozzle outlet andhaving a straight elongated portion adjacent to the outennozzle outletand of constant cross section corresponding to that of the finishedsheath, said tapering portion of said outer-nozzle bore extendingcoaxially and symmetrically to said inner-nozzle tube at a locationalong said tube, said tube outlet being axially spaced from thenarrowest cross section of said tapering portion of said outernozzlebore, and said bore having between its portion of constant cross sectionand said tube outlet a maximum taper smaller in the diametricaldirection and longer in the axial direction than the diameter of saidconstant cross section.

7. In apparatus for manufacturing pencils according to claim 6, saidoutlet of said inner-nozzle tube being located within said outer-nozzlebore portion of constant cross section, and said latter bore portionhaving most of its axial length extend beyond said tube outlet.

8. In apparatus for manufacturing pencilstaccording to claim 6, saidmarking-medium supply means comprising an inner feed screw coaxiallylocated within said feedscrew means for said sheath material, astationary sleeve disposed coaxially between said feed-screw means andsaid inner feed screw and coaxially joined with said inner nozzle, saidsleeve having channel means extending along said inner feed screw forheat-control medium; and a sleeve coaxially enclosing said outer nozzleand having fluid-channel means constituting said temperature controlmeans.

9. In apparatus for manufacturing pencils according to claim 6, saidcore-material feed means comprising an inlet member having a ductcoaxially aligned with the interior of said nozzle tube for supplyingsaid marking medium in form of a pre-shaped rigid core body; furthernozzle means having a cavity surrounding said duct in said inlet member,and further feed means communicating with said cavity for supplyingadhesive thereto, whereby said core body is adhesively coated whenentering said nozzle tube.

10. In apparatus for manufacturing pencils according to claim 6, saidouter nozzle having lateral openings extending from said taperingportion of said outer-nozzle bore to the outside, and respectiveadjustable pressure relief valves normally closing said openings topermit escape of sheath material when the pressure in said sheathmaterial within said bore reaches an adjusted value.

11. In an apparatus according to claim 6, said outer nozzle having atubular wall tapering toward the outernozzle, outlet to a line edgehaving the shape and size of the sheath of the pencil; and a coatingnozzle coaxial with said other two nozzles and surrounding said tubularwall and line edge of said outer nozzle, continuous feed means connectedwith said coating nozzle for supplying thermoplastic coating materialthereto; said coating nozzle having a straight outlet portion ofconstant inner cross section corresponding to that of the finishedpencil and having another portion adjacent to said outlet portion andtapering toward said outlet portion, the outlet of said outer nozzlebeing axially spaced from the narrowest cross section of said taperingportion of said coating nozzle.

12. In apparatus according to claim 11, said coating nozzle having alateral opening extending from said taperingportion of said coatingnozzle to the outside, and a pressure relief valve normally closing saidopening to permit escape of coating material when the pressure in saidoutlet portion exceeds a given value.

References Cited in the file of this patent UNITED STATES PATENTS253,822 Mignon Feb. 14, 1882 484,777 Chase Oct. 25, 1892 876,755 WebbJan. 14, 1908 936,722 Howard Oct. 12, 1909 1,630,451 Ray May 31, 19271,646,825 Kochendorfer July 25, 1927 1,649,892 Daniels Nov. 22, 19271,978,163 Megow Oct. 23, 1934 2,401,551 Cook June 4, 1946

